U.S. patent application number 11/469253 was filed with the patent office on 2008-03-06 for light recycling system with an inorganic, dielectric grid polarizer.
Invention is credited to Eric Gardner, Douglas P. Hansen, Raymond T. Perkins, Bin Wang.
Application Number | 20080055721 11/469253 |
Document ID | / |
Family ID | 39151113 |
Filed Date | 2008-03-06 |
United States Patent
Application |
20080055721 |
Kind Code |
A1 |
Perkins; Raymond T. ; et
al. |
March 6, 2008 |
Light Recycling System with an Inorganic, Dielectric Grid
Polarizer
Abstract
A light recycling system includes a light source capable of
producing a visible light beam. An inorganic, dielectric grid
polarizing beam splitter is disposable in the light beam to
separate the light beam into two light beams of orthogonal
polarization orientation including a transmitted beam and a
reflected beam. The grid polarizer includes a stack of film layers
disposed over the substrate. Each film layer is formed of a
material that is both inorganic and dielectric. Adjacent film
layers have different refractive indices. At least one of the film
layers is discontinuous to form a form birefringent layer with an
array of parallel ribs with a period less than approximately 260
nm. Light reorientation means is disposable in the transmitted or
reflected beam for changing the polarization orientation of the
transmitted or reflected beam.
Inventors: |
Perkins; Raymond T.; (Orem,
UT) ; Wang; Bin; (Orem, UT) ; Gardner;
Eric; (Eagle Mountain, UT) ; Hansen; Douglas P.;
(Spanish Fork, UT) |
Correspondence
Address: |
THORPE NORTH & WESTERN, LLP.
8180 SOUTH 700 EAST, SUITE 350
SANDY
UT
84070
US
|
Family ID: |
39151113 |
Appl. No.: |
11/469253 |
Filed: |
August 31, 2006 |
Current U.S.
Class: |
359/485.04 ;
359/485.05; 359/489.06 |
Current CPC
Class: |
G02B 27/283 20130101;
G02B 5/3008 20130101 |
Class at
Publication: |
359/486 |
International
Class: |
G02B 5/30 20060101
G02B005/30 |
Claims
1. A light recycling system, comprising: a) a light source capable
of producing a visible light beam; b) an inorganic, dielectric grid
polarizing beam splitter disposable in the light beam to separate
the light beam into two light beams of orthogonal polarization
orientation including a transmitted beam and a reflected beam,
comprising: i) a substrate; ii) a stack of film layers disposed
over the substrate; iii) each film layer being formed of a material
that is both inorganic and dielectric; iv) adjacent film layers
having different refractive indices including lower and higher
refractive indices; v) the bottom layer adjacent the substrate
having a lower refractive index lss than a higher refractive index
of an adjacent layer; vi) at least one of the film layers being
discontinuous to form a form birefringent layer with an array of
parallel ribs with a period less than approximately 260 nm; vii) at
leat two adjacent film layers including a continuous layer covering
the substrate and a discontinuous layer; viii) the polarizer device
consisting of only inorganic and dielectric materials; and ix) at
least one discontinuous layer being disposed intermediate the
substrate and continuous layer; c) light reorientation means
disposable in the transmitted or reflected beam for changing the
polarization orientation of the transmitted or reflected beam.
2. A system in accordance with claim 1, wherein the material of
each film layer is optically transmissive to visible light.
3. A system in accordance with claim 2, wherein the material of
each film layer has negligible absorption of visible light.
4. A system in accordance with claim 1, wherein the material of at
least one of the film layers is naturally birefringent.
5. A system in accordance with claim 1, wherein the film layers
alternate between higher and lower refractive indices.
6. (canceled)
7. A system in accordance with claim 1, wherein the polarizer
device is formed without any organic or electrically conductive
material.
8. A system in accordance with claim 1, wherein all of the film
layers are discontinuous and form the array of parallel ribs.
9. A system in accordance with claim 1, wherein at least two
adjacent film layers include a continuous layer and a discontinuous
layer.
10. A system in accordance with claim 1, further comprising: light
combination means disposable in the transmitted or reflected beam
for changing a direction of the transmitted or reflected beam so
that both the transmitted beam and the reflected beam are combined
and have the same direction.
11. A light recycling system, comprising: a) a light source capable
of producing a visible light beam; b) an inorganic, dielectric grid
polarizing beam splitter disposable in the light beam to separate
the light beam into two light beams of orthogonal polarization
orientation including a transmitted beam and a reflected beam,
comprising: i) a substrate; ii) a stack of film layers disposed
over the substrate including a bottom layer disposed adjacent the
substrate; iii) each film layer being formed of a material that is
both inorganic and dielectric; iv) adjacent film layers having
different refractive indices including lower and higher refractive
indices; v) the bottom layer adjacent the substrate having a lower
refractive index less than a higher refractive index of an adjacent
layer; vi) at least one of the film layers being discontinuous to
form a form birefringent layer with an array of parallel ribs with
a period less than approximately 260 nm; vii) at least two adjacent
film layers including a continuous layer covering the substrate and
a discontinuous layer; viii) the polarizer device consisting of
only inorganic and dielectric materials; and c) light combination
means disposable in the transmitted or reflected beam for changing
a direction of the transmitted or reflected beam so that both the
transmitted beam and the reflected beam are combined and have the
same direction.
12. A system in accordance with claim 11, wherein the material of
each film layer is optically transmissive to visible light.
13. A system in accordance with claim 12, wherein the material of
each film layer has negligible absorption of visible light.
14. A system in accordance with claim 11, wherein the material of
at least one of the film layers is naturally birefringent.
15. A system in accordance with claim 11, wherein the film layers
alternate between higher and lower refractive indices.
16. (canceled)
17. A system in accordance with claim 11, wherein the polarizer
device is formed without any organic or electrically conductive
material.
18. A system in accordance with claim 11, wherein all of the film
layers are discontinuous and form the array of parallel ribs.
19. A system in accordance with claim 11, wherein at least two
adjacent film layers include a continuous layer and a discontinuous
layer.
20. A system in accordance with claim 11, further comprising: light
reorientation means disposable in the transmitted or reflected beam
for changing the polarization orientation of the transmitted or
reflected beam.
21. A light recycling system, comprising: a) a light source capable
of producing a visible light beam; b) an inorganic, dielectric grid
polarizing beam splitter disposable in the light beam to separate
the light beam into two light beams of orthogonal polarization
orientation including a transmitted beam and a reflected beam,
comprising: i) a substrate; ii) a stack of film layers disposed
over the substrate including a bottom discontinuous layer disposed
adjacent the substrate; iii) each film layer being formed of a
material that is both inorganic and dielectric; iv) adjacent film
layers having different refractive indices including lower and
higher refractive indices; and v) the bottom layer adjacent the
substrate having a lower refractive index less than a higher
refractive index if an adjacent layer; vi) at least one of the film
layers being discontinuous to form a form birefringent layer with
an array of parallel ribs with a period less than approximately 260
nm; vii) at least two adjacent film layer include a continuous
layer covering the substrate and discontinuous layer; and viii) the
polarizer device consisting of only inorganic and dielectric
materials; and c) light reorientation means disposable in the
transmitted or reflected beam for changing the polarization
orientation of the transmitted or reflected beam; and d) light
combination means disposable in the transmitted or reflected beam
for changing a direction of the transmitted or reflected beam so
that both the transmitted beam and the reflected beam are combined
and have the same direction.
22. A system in accordance with claim 21, wherein the grid
polarizing beam splitter further comprises: at least two adjacent
film layers including a continuous layer covering the substrate and
a discontinuous layer.
23. A device in accordance with claim 1, further comprising a
plurality of ribs formed in and extending from the substrate.
24. A device in accordance with claim 1, wherein the stack of film
layers includes top and bottom layers and intervening layers; and
wherein the bottom layer has a thickness less than a thickness of
the intervening layers.
25. A device in accordance with claim 11, further comprising a
plurality of ribs formed in and extending from the substrate.
26. A device in accordance with claim 11, wherein the stack of film
layers includes top and bottom layers and intervening layers; and
wherein the bottom layer has a thickness less than a thickness of
the intervening layers.
Description
RELATED APPLICATIONS
[0001] This is related to U.S. patent application Ser. No. ______,
filed Aug. 31, 2006, entitled "Inorganic, Dielectric Grid
Polarizer" as attorney docket no. 00546-32517.A; U.S. patent
application Ser. No. ______, filed Aug. 31, 2006, entitled
"Projection Display with an Inorganic, Dielectric Grid Polarizer"
as attorney docket no. 00546-32517.B; U.S. patent application Ser.
No. ______, filed Aug. 31, 2006, entitled "Optical Data Storage
System with an Inorganic, Dielectric Grid Polarizer" as attorney
docket no. 00546-32517.C; U.S. patent application Ser. No. ______,
filed Aug. 31, 2006, entitled "Optical Polarization Beam
Combiner/Splitter with an Inorganic, Dielectric Grid Polarizer" as
attorney docket no. 00546-32517.E which are herein incorporated by
reference.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention relates generally to a light recycling
system with an inorganic, dielectric grid polarizer or polarizing
beam splitter.
[0004] 2. Related Art
[0005] Various types of polarizers or polarizing beam splitters
(PBS) have been developed for polarizing light, or separating
orthogonal polarization orientations of light. A MacNeille PBS is
based upon achieving Brewster's angle behavior at the thin film
interface along the diagonal of the high refractive index cube in
which it is constructed. Such MacNeille PBSs generate no
astigmatism, but have a narrow acceptance angle, and have
significant cost and weight.
[0006] Another polarizing film includes hundreds of layers of
polymer material stretched to make the films birefringent. Such
stretched films have relatively high transmission contrast, but not
reflection contrast. In addition, polymer materials are organic and
not as capable of withstanding higher temperatures or higher energy
flux. For example, see Vikuiti.TM. polarizing films by 3M.
[0007] Visible light wire-grid polarizers or polarizing beam
splitters have been developed and successfully incorporated into
rear projection monitors or televisions. For example, see U.S. Pat.
Nos. 6,234,634 and 6,447,120. A wire-grid polarizer can have an
array of parallel conductive wires with a period less than the
wavelength of visible light. The conductive metal of the wires,
however, can absorb light.
[0008] Composite wire-grid polarizers have been proposed in which
the wires include alternating layers of dielectric and conductive
layers. For example, see U.S. Pat. Nos. 6,532,111; 6,665,119 and
6,788,461. Such polarizers, however, still have conductive
materials.
[0009] Polarizing beam splitters have been proposed for the
infrared wavelengths (1300-1500 nm), but such beam splitters are
formed of material that absorb visible light, and thus are
inoperable in the visible spectrum. See R.-C. Tyan, P.-C. Sun, and
Y. Fainman, "Polarizing beam splitters constructed of
form-birefringent multilayer gratings", SPIE Proceedings:
Diffractive and Holographic Optics Technology III, Vol. 2689, 82-89
(1996).
SUMMARY OF THE INVENTION
[0010] It has been recognized that it would be advantageous to
develop a polarizer or polarizing beam splitter that has high
contrast in reflection and/or transmission, can withstand high
temperatures and/or high energy flux, and that is simpler to
manufacture. In addition, it has been recognized that it would be
advantageous to develop a polarizer that is inorganic and
dielectric. Furthermore, it has been recognized that it would be
advantageous to develop a light recycling system utilizing such a
polarizer or polarizing beam splitter.
[0011] The invention provides a light recycling system with a light
source capable of producing a visible light beam. An inorganic,
dielectric grid polarizing beam splitter is disposable in the light
beam to separate the light beam into two light beams of orthogonal
polarization orientation including a transmitted beam and a
reflected beam. The grid plarizer includes a stack of film layers
disposed over a substrate. Each film layer being formed of a
material that is both inorganic and dielectric. Adjacent film
layers have different refractive indices. At least one of the film
layers is discontinuous to form a form birefringent layer with an
array of parallel ribs with a period less than approximately 260
nm.
[0012] In accordance with one aspect of the present invention,
light reorientation means is disposable in the transmitted or
reflected beam for changing the polarization orientation of the
transmitted or reflected beam.
[0013] In accordance with another aspect of the present invention,
light combination means is disposable in the transmitted or
reflected beam for changing a direction of the transmitted or
reflected beam so that both the transmitted beam and the reflected
beam are combined and have the same direction.
[0014] In accordance with another aspect of the present invention,
both light reorientation means and light combination means are
included.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Additional features and advantages of the invention will be
apparent from the detailed description which follows, taken in
conjunction with the accompanying drawings, which together
illustrate, by way of example, features of the invention; and,
wherein:
[0016] FIG. 1 is a cross-sectional schematic side view of an
inorganic, dielectric grid polarizer or polarizing beam splitter in
accordance with an embodiment of the present invention;
[0017] FIG. 2 is a cross-sectional schematic side view of another
inorganic, dielectric grid polarizer or polarizing beam splitter in
accordance with another embodiment of the present invention;
[0018] FIG. 3 is a cross-sectional schematic side view of another
inorganic, dielectric grid polarizer or polarizing beam splitter in
accordance with another embodiment of the present invention;
[0019] FIG. 4 is a cross-sectional schematic side view of another
inorganic, dielectric grid polarizer or polarizing beam splitter in
accordance with another embodiment of the present invention;
[0020] FIG. 5 is a cross-sectional schematic side view of another
inorganic, dielectric grid polarizer or polarizing beam splitter in
accordance with another embodiment of the present invention;
[0021] FIG. 6 is a cross-sectional schematic side view of another
inorganic, dielectric grid polarizer or polarizing beam splitter in
accordance with another embodiment of the present invention;
[0022] FIG. 7 is a schematic view of a method for making the
polarizer or polarizing beam splitter of FIG. 1 (or FIG. 4 or 5 or
6);
[0023] FIG. 8 is a schematic view of a method for making the
polarizer or polarizing beam splitter of FIG. 2 (or FIG. 3);
[0024] FIGS. 9a-c are schematic side views of examples of the
inorganic, dielectric grid polarizers of FIG. 1;
[0025] FIG. 10 is a schematic view of a projection display system
in accordance with an embodiment of the present invention;
[0026] FIG. 11 is a schematic view of a modulation optical system
in accordance with an embodiment of the present invention;
[0027] FIG. 12 is a schematic view of a projection display system
in accordance with an embodiment of the present invention;
[0028] FIG. 13 is a schematic view of a projection display system
in accordance with an embodiment of the present invention;
[0029] FIG. 14 is a schematic view of another projection display
system in accordance with an embodiment of the present
invention;
[0030] FIG. 15 is a schematic view of another projection display
system in accordance with an embodiment of the present
invention;
[0031] FIG. 16 is a schematic view of another modulation optical
system in accordance with an embodiment of the present
invention;
[0032] FIG. 17 is a cross-sectional schematic side view of another
inorganic, dielectric grid polarizer or polarizing beam splitter in
accordance with another embodiment of the present invention;
[0033] FIGS. 18a and 18b are schematic views of a combiner and a
splitter in accordance with an embodiment of the present
invention;
[0034] FIG. 19 is a cross-sectional schematic side view of another
inorganic, dielectric grid polarizer or polarizing beam splitter in
accordance with another embodiment of the present invention;
[0035] FIG. 20 is a schematic view of an optical storage system in
accordance with an embodiment of the present invention; and
[0036] FIGS. 21a-d are schematic views light recycling systems
using a grid polarizer in accordance with an embodiment of the
present invention.
[0037] Various features in the figures have been exaggerated for
clarity.
[0038] Reference will now be made to the exemplary embodiments
illustrated, and specific language will be used herein to describe
the same. It will nevertheless be understood that no limitation of
the scope of the invention is thereby intended.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENT(S)
Definitions
[0039] The terms polarizer and polarizing beam splitter are used
interchangeably herein.
[0040] The term dielectric is used herein to mean non-metallic.
Description
[0041] It has been recognized that wire-grid polarizers can provide
enhanced performance or contrast to projection display systems,
such as rear projection display systems. In addition, it has been
recognized that that the conductive wires of a wire-grid polarizer
can absorb light and can heat-up. Furthermore, it has been
recognized that multi-layer stretched film polarizers are difficult
to fabricate.
[0042] As illustrated in FIG. 1, an inorganic, dielectric grid
polarizer, or polarizing beam splitter, indicated generally at 10,
is shown in an exemplary implementation in accordance with the
present invention. The polarizer 10 can include a stack 14 of film
layers 18a-18f disposed over a substrate 22. The substrate 22 can
be formed of an inorganic and dielectric material, such as BK7
glass. In addition, the film layers 18a-18f, and thus the stack 14,
can be formed of inorganic and dielectric materials. Thus, the
entire polarizer can be inorganic and dielectric, or formed of only
inorganic and dielectric materials.
[0043] In addition, the dielectric material can further be
optically transmissive with respect to the incident light.
Furthermore, the dielectric material can further have negligible
absorption. Thus, the light incident on the grid polarizer is not
absorbed, but reflected and transmitted.
[0044] The material of each film layer can have a refractive index
n. Adjacent film layers have different refractive indices
(n.sub.1.noteq.n.sub.2). In one aspect, film layers alternate
between higher and lower refractive indices (for example
n.sub.1<n.sub.2>n.sub.3; n.sub.1>n.sub.2<n.sub.3;
n.sub.1<n.sub.2<n.sub.3 or n.sub.1>n.sub.2>n.sub.3). In
addition, the first film layer 18a can have a different refractive
index n.sub.1 than the refractive index n.sub.s of the substrate 22
(n.sub.1.noteq.n.sub.s). The stack of film layers can have a basic
pattern of two or more layers with two or more reflective indices,
two or more different thicknesses, and two or more different
materials. This basic pattern can be repeated.
[0045] In addition, the thickness of each layer can be tailored to
transmit substantially all light of p-polarization orientation, and
to reflect substantially all light of s-polarization orientation.
Therefore, while the thicknesses t.sub.1-6 shown in the figures are
the same, it will be appreciated that they can be different.
[0046] While the stack 14 is shown with six film layers 18a-f, it
will be appreciated that the number of film layers in the stack can
vary. In one aspect, the stack can have between three and twenty
layers. It is believed that less than twenty layers can achieve the
desired polarization. In addition, while the film layers are shown
as having the same thickness, it will be appreciated that the
thicknesses of the film layers can very, or can be different. The
thickness of all the film layers in the stack over the substrate
can be less than 2 micrometers.
[0047] At least one of the film layers is discontinuous to form a
form birefringent layer with an array 26 of parallel ribs 30. The
ribs have a pitch or period P less than the wavelength being
treated, and in one aspect less than half the wavelength being
treated. For visible light applications (.lamda..apprxeq.400-700
nm), such as projection display systems, the ribs can have a pitch
or period less than 0.35 microns or micrometers (0.35 .mu.m or 350
nm) for visible red light (.lamda..apprxeq.700 nm) in one aspect;
or less than 0.20 microns or micrometers (0.20 .mu.m or 200 nm) for
all visible light in another aspect. For infrared applications
(.lamda..apprxeq.1300-1500 nm), such as telecommunication systems,
the ribs can have a pitch or period less than 0.75 micron or
micrometer (0.75 .mu.m or 750 nm) in one aspect, or less than 0.4
microns or micrometers (0.40 .mu.m or 400 nm) in another aspect.
Thus, an incident light beam L incident on the polarizer 10
separates the light into two orthogonal polarization orientations,
with light having s-polarization orientation (polarization
orientation oriented parallel to the length of the ribs) being
reflected, and light having p-polarization orientation
(polarization orientation oriented perpendicular to the length of
the ribs) being transmitted or passed. (It is of course understood
that the separation, or reflection and transmission, may not be
perfect and that there may be losses or amounts of undesired
polarization orientation either reflected and/or transmitted.) In
addition, it will be noted that the array or grid of ribs with a
pitch less than about half the wavelength of light does not act
like a diffraction grating (which has a pitch about half the
wavelength of light). Thus, the grid polarizer avoids diffraction.
Furthermore, it is believed that such periods also avoid resonant
effects or anomalies.
[0048] As shown in FIG. 1, all of the film layers are discontinuous
and form the array 26 of parallel ribs 30. The ribs 30 can be
separated by intervening grooves 34 or troughs. In this case, the
grooves 34 extend through all the film layers 18a-18f to the
substrate 22. Thus, each rib 30 is formed of a plurality of layers.
In addition, all the film layers are form birefringent. As
discussed below, such a configuration can facilitate
manufacture.
[0049] The grooves 34 can be unfilled, or filed with air (n=1).
Alternatively, the grooves 34 can be filled with a material that is
optically transmissive with respect to the incident light.
[0050] In one aspect, a thickness of all the film layers in the
stack over the substrate is less than 2 microns. Thus, the grid
polarizer 10 can be thin for compact applications, and can be
thinner than many multi-layered stretched film polarizers that have
hundreds of layers.
[0051] It is believed that the birefringent characteristic of the
film layers, and the different refractive indices of adjacent film
layers, causes the grid polarizer 10 to substantially separate
polarization orientations of incident light, substantially
reflecting light of s-polarization orientation, and substantially
transmitting or passing light of p-polarization orientation. In
addition, it is believed that the number of film layers, thickness
of the film layers, and refractive indices of the film layers can
be adjusted to vary the performance characteristics of the grid
polarizer.
[0052] Referring to FIG. 2, another inorganic, dielectric grid
polarizer, or polarizing beam splitter, indicated generally at 10b,
is shown in an exemplary implementation in accordance with the
present invention. The above description is incorporated by
reference. The polarizer 10b includes a stack 14b of both
discontinuous layers 38a-38c and continuous layers 42a-42c. In one
aspect, the discontinuous and continuous layers can alternate, as
shown. Having one or more continuous layers can provide structural
support to the grid, particularly if the ribs are tall. In another
aspect, the ribs of one layer can be aligned with the ribs of
another layer as shown. Alternatively, a polarizer 10c can have the
ribs of one layer be off-set with respect to the ribs of another
layer, as shown in FIG. 3. It is believed that the ribs can be
aligned or off-set in order to tune or configure the grid polarizer
10b or 10c for a particular angle of incidence. For example,
aligned ribs may be better suited for normal incident light, while
the off-set ribs may be better suited for angled incident
light.
[0053] In one aspect, the continuous layers can be formed of a
material that is naturally birefringent, as opposed to form
birefringent. Thus, the entire stack of thin film layers can be
birefringent, without having to form ribs in the layers of
naturally birefringent material.
[0054] Referring to FIGS. 4 and 5, other inorganic, dielectric grid
polarizers or polarizing beam splitters, indicated generally at 10d
and 10e, are shown in exemplary implementations in accordance with
the present invention. The above description is incorporated by
reference. The polarizer 10d can have multiple discontinuous layers
separate by one or more continuous layers. In addition, the
polarizer 10d can be similar to two polarizers described in FIG. 1
stacked one atop the other. The ribs can be aligned as in FIG. 4,
or offset as in FIG. 5.
[0055] Referring to FIG. 6, another inorganic, dielectric grid
polarizer, or polarizing beam splitter, indicated generally at 10f,
is shown in an exemplary implementation in accordance with the
present invention. The above description is incorporated by
reference. The polarizer includes a plurality of ribs 38 formed in
and extending from the substrate 22f itself. Thus, the ribs 30
formed in the film layers or the stack 14 of film layers can be
disposed over or carried by the ribs 38 of the substrate. The ribs
38 of the substrate can define intervening grooves or troughs 42
that can be aligned with the grooves 34 of the film layers. With
this configuration, a portion of the substrate 22f can form a form
birefringent layer. The ribs 38 or grooves 42 can be formed by
etching the substrate 22f, such as by over-etching the above
layers.
[0056] Referring to FIG. 7, a method is illustrated for forming an
inorganic, dielectric grid polarizer, such as those shown in FIGS.
1, 4, 5 or 6. A substrate 22 is obtained or provided. As described
above, the substrate 22 can be BK7 glass. In one aspect, the
substrate is transparent to the desired wavelength of
electromagnetic radiation. The substrate may be cleaned and
otherwise prepared. A first continuous layer 46 is formed over the
substrate 22 with a first inorganic, dielectric material having a
first refractive index. A second continuous layer 48 is formed over
the first continuous layer 46 with a second inorganic, dielectric
material having a second refractive index. Subsequent continuous
layers 50 can be formed over the second layer. The first and second
layers 46 and 48, as well as the subsequent layers, can be formed
by deposition, chemical vapor deposition, spin coating, etc., as is
known in the art. The continuous layers, or at least one of the
first or second continuous layers, are patterned to create a
discontinuous layer 18a or 18b with an array of parallel ribs 30
defining at least one form birefringent layer. In addition, all the
continuous layers can be patterned to create all discontinuous
layers 18a-f. The layers can be patterned by etching, etc., as is
known in the art.
[0057] The grid polarizer can be disposed in a beam of light and
can reflect light of substantially s-polarization orientation and
transmit light of substantially p-polarization orientation.
[0058] Referring to FIG. 8, another method is illustrated for
forming an inorganic, dielectric grid polarizer, such as those
shown in FIGS. 2, 3, 4 or 5. The method is similar to the method
described above which incorporated by reference. A substrate 22 is
obtained or provided. A first continuous layer 46 is formed over
the substrate 22 with a first inorganic, dielectric material having
a first refractive index. The first continuous layer 46 can be
patterned to create a discontinuous layer 38a with an array of
parallel ribs 30 defining at least one form birefringent layer. A
second continuous layer 42a is formed over the first discontinuous
layer 38a with a second inorganic, dielectric material having a
second refractive index. Another continuous layers 54 can be formed
over the second layer, and patterned to form a second discontinuous
layer 38b. Thus, patterning includes patterning less than all of
the layers so that at least two adjacent layers include a
continuous layer and a discontinuous layer.
[0059] In another aspect, the second continuous layer can be formed
over the first, and the second continuous layer patterned.
EXAMPLE 1
[0060] Referring to FIG. 9a, a first non-limiting example of an
inorganic, dielectric grid polarizer is shown.
[0061] The grid polarizer has a stack of fifteen film layers
disposed over a substrate. The film layers are formed of inorganic
and dielectric materials, namely alternating layers of silicon
dioxide (SiO.sub.2)(n=1.45) and titanium dioxide
(TiO.sub.2)(n=2.5). The bottom layer and the top layer are silicon
dioxide. Thus, the layers alternate between higher and lower
indices of refraction (n). The top and bottom layers have a
thickness (t.sub.1 and t.sub.15) of 35 nm, while the intervening
layers have a thickness (t.sub.2-14) of 71 nm. Thus, the entire
stack has a thickness (t.sub.total) of approximately 1 .mu.m or
micron. All of the film layers are discontinuous and form an array
26 of parallel ribs 30. Thus, all of the layers are discontinuous
to form form birefringent layers. The ribs have a pitch or period
(p) of 180 nm, and a duty cycle (ratio of period to width) of 0.5
or width (w) of 90 nm.
[0062] Table 1 shows the calculated performance for the grid
polarizer of FIG. 9a with incident light with a wavelength
(.lamda.) of 450 nm at angles of incidence of 30.degree.,
45.degree. and 60.degree..
TABLE-US-00001 TABLE 1 Example 1 Incident Angle 30 45 60 Wavelength
450 p-transmission (Tp) 98.43% 99.18% 95.33% p-reflection (Rp)
1.5622% 0.8152% 4.67% s-transmission (Ts) 0.1594% 0.0517% 0.0171%
s-reflection (Rs) 99.84% 99.94% 99.98% Efficiency (white)(TpRs)
98.27% 99.12% 95.31% Efficiency (black)(TpRp) 1.54% 0.81% 4.45%
Contrast Transmission (T) 618 1,920 5,575 Contrast Reflection (R)
64 123 21
From Table 1, it can be seen that the grid polarizer has excellent
efficiency (TpRs). In addition, it can be seen that the
transmission contrast varies with angle of incidence, exhibiting
good contrast at 60.degree. with a reduction in efficiency. At
45.degree., the grid polarizer has excellent efficiency and
acceptable contrast for many applications.
EXAMPLE 2
[0063] Referring to FIG. 9b, a second non-limiting example of an
inorganic, dielectric grid polarizer is shown.
[0064] The grid polarizer has a stack of fifteen film layers
disposed over a substrate. The film layers are formed of inorganic
and dielectric materials, namely alternating layers of silicon
dioxide (SiO.sub.2)(n=1.45) and titanium dioxide
(TiO.sub.2)(n=2.5). The bottom layer and the top layer are silicon
dioxide. Thus, the layers alternate between higher and lower
indices of refraction (n). The top and bottom layers have a
thickness (t.sub.1 and t.sub.15) of 53 nm, while the intervening
layers have a thickness (t.sub.2-14) of 106 nm. Thus, the entire
stack has a thickness (t.sub.total) of approximately 1.5 .mu.m or
microns. All of the film layers are discontinuous and form an array
26 of parallel ribs 30. Thus, all of the layers are discontinuous
to form form birefringent layers. The ribs have a pitch or period
(p) of 260 nm, and a duty cycle (ratio of period to width) of 0.5
or width (w) of 130 nm.
[0065] Table 2 shows the calculated performance for the grid
polarizer of FIG. 9b with incident light with a wavelength
(.lamda.) of 650 nm at angles of incidence of 30.degree.,
45.degree. and 60.degree..
TABLE-US-00002 TABLE 2 Example 2 Incident Angle 30 45 60 Wavelength
650 p-transmission (Tp) 98.53% 99.74% 96.66% p-reflection (Rp)
1.4685% 0.2567% 3.3318% s-transmission (Ts) 0.2315% 0.0528% 0.0133%
s-reflection (Rs) 99.76% 99.94% 99.98% Efficiency (white)(TpRs)
98.29% 99.68% 96.64% Efficiency (black)(TpRp) 1.45% 0.26% 3.22%
Contrast Transmission (T) 426 1,889 7,246 Contrast Reflection (R)
68 389 30
From Table 2, it can again be seen that the grid polarizer has
excellent efficiency (TpRs). In addition, it can be seen that the
transmission contrast varies with angle of incidence, exhibiting
good contrast at 60.degree. with a reduction in efficiency. At
45.degree., the grid polarizer has excellent efficiency and
acceptable contrast for many applications.
EXAMPLE 3
[0066] Referring to FIG. 9c, a third non-limiting example of an
inorganic, dielectric grid polarizer is shown.
[0067] The grid polarizer has a stack of fifteen film layers
disposed over a substrate. The film layers are formed of inorganic
and dielectric materials, namely alternating layers of silicon
dioxide (SiO.sub.2)(n=1.45) and titanium dioxide
(TiO.sub.2)(n=2.5). The bottom layer and the top layer are silicon
dioxide. Thus, the layers alternate between higher and lower
indices of refraction (n). The top and bottom layers have a
thickness (t.sub.1 and t.sub.15) of 44 nm, while the intervening
layers have a thickness (t.sub.2-14) of 88 nm. Thus, the entire
stack has a thickness (t.sub.total) of approximately 1.2 .mu.m or
micron. All of the film layers are discontinuous and form an array
26 of parallel ribs 30. Thus, all of the layers are discontinuous
to form form birefringent layers. The ribs have a pitch or period
(p) of 230 nm, and a duty cycle (ratio of period to width) of 0.5
or width (w) of 115 nm.
[0068] Table 3 shows the calculated performance for the grid
polarizer of FIG. 9c with incident light with a wavelength
(.lamda.) of 550 nm at angles of incidence of 30.degree.,
45.degree. and 60.degree..
TABLE-US-00003 TABLE 3 Example 3 Incident Angle 30 45 60 Wavelength
550 p-transmission (Tp) 97.93% 99.02% 95.81% p-reflection (Rp)
2.0656% 0.9795% 4.1840% s-transmission (Ts) 0.1325% 0.0456% 0.0000%
s-reflection (Rs) 99.86% 99.95% 100% Efficiency (white)(TpRs)
97.79% 98.97% 95.81% Efficiency (black)(TpRp) 2.02% 0.97% 4.01%
Contrast Transmission (T) 739 2,171 Very high* Contrast Reflection
(R) 48 102 24 *Difficult to accurately calculate.
From Table 3, it can be seen that the grid polarizer has excellent
efficiency (TpRs). In addition, it can be seen that the
transmission contrast varies with angle of incidence, exhibiting
good contrast at 60.degree. with a reduction in efficiency. At
45.degree., the grid polarizer has excellent efficiency and
acceptable contrast for many applications.
[0069] From the above examples, it can be seen that the thicknesses
of the layers can be tailored to a desired wavelength. It will be
noted that the thickness of the layers increased for larger
wavelengths. Similarly, it can be seen that the period can be
increased for larger wavelengths. Furthermore, the above examples
show that an effective visible grid polarizer can have a period
less than 260 nm and can be operable over the visible spectrum.
[0070] Referring to FIG. 10, a projection display system 100
utilizing inorganic, dielectric polarizing beam splitters 102 is
shown in accordance with the present invention. The polarizing beam
splitters 102 can be any described above. The system 100 includes a
light source 104 to produce a light beam. The light beam can be any
appropriate type, as known in the art, including an arc light, an
LED array, etc. The beam can be treated by various optics,
including beam shaping optics, recycling optics, polarizing optics,
etc. (Various aspects of using a wire-grid polarizer in light
recycling are shown in U.S. Pat. Nos. 6,108,131 and 6,208,463;
which are herein incorporated by reference.) In addition, a light
recycling system is described below. A polarizing beam splitter 102
may also be incorporated into the light recycling. One or more
color separator(s) 108, such as dichroic filters, can be disposable
in the light beam to separate the light beam into color light
beams, such as red, green and blue.
[0071] At least one beam splitter 102 can be disposable in one of
the color light beams to transmit a polarized color light beam. At
least one reflective spatial light modulator 112, such as an LCOS
panel, can be disposable in the polarized color light beam to
encode image information thereon to produce an image bearing color
light beam. The beam splitter 102 can be disposable in the image
bearing color light beam to separate the image information and to
reflect a polarized image bearing color light beam. As shown, three
beam splitters 102 and three spatial light modulators 112 can be
used, one for each color of light (blue, green, red). The polarized
image bearing color light beams can be combined with an image
combiner, such as an X-cube or recombination prism 116. Projection
optics 120 can be disposable in the polarized image bearing color
light beam to project the image on a screen 124.
[0072] The projection display system 100 can be a three-channel or
three-color system which separates and treats three different color
beams, such as red, green and blue, as described above. Thus, the
system can use three polarizing beam splitters 102. The beam
splitters 102 can be the same and can be configured to operate
across the visible spectrum. Alternatively, two or more of the beam
splitters 102 may be tuned to operate with a particular color or
wavelength of light. For example, the display system 100 can have
two or three different beam splitters (such as those similar to
Examples 103 described above) each configured or tuned to operate
with one or two colors or wavelengths.
[0073] The polarizing beam splitters 102 can face, or can have an
image side that faces, the spatial light modulator 112. The facing
or image side is opposite the substrate on which the wire-grid is
disposed, or the side with the film layers. It is believed
desirable to reflect the image from the grid side of the beam
splitter to avoid distortion of the image beam that might occur
with passing the image through the substrate.
[0074] The inorganic, dielectric grid polarizing beam splitter 102
of the present invention reduces heat transfer associated with
conductive materials. Thus, it is believed that the beam splitter
can be disposed adjacent to, or even abutting to, other components
without transferring as much heat to those components. In addition,
use of the beam splitter is believed to reduce thermal stress
induced birefringence.
[0075] Referring to FIG. 11, it will be appreciated that the beam
splitter 102 described above can be used in a subsystem of the
projection display, such as a light engine or a modulation optical
system 150, which includes the spatial light modulator 112 and beam
splitter 102. Such a modulation optical system may also include a
light source, color separators, beam shaping optics, light
recycler, pre-polarizers, post-polarizers, and/or an x-cube. One or
more modulation optical systems can be combined with other optics
and components in a projection system.
[0076] As described above, the reflective spatial light modulator
112 can be configured to selectively encode image information on a
polarized incident light beam to encode image information on a
reflected beam. The beam splitter 102 can be disposed adjacent the
reflective spatial light modulator to provide the polarized
incident light beam to the reflective spatial light modulator, and
to separate the image information from the reflected beam.
[0077] Although a three-channel, or three-color, projection system
has been described above, it will be appreciated that a display
system 150, 150b, 160, 164 or 164b can have a single channel, as
shown in FIGS. 11-14 and 16. Alternatively, the single channels
shown in FIGS. 11-14 and 16 can be modulated so that multiple
colors are combined in a single channel. In addition, although the
grid polarizer has been described above as being used with a
reflective spatial light modulator, such as an LCOS panel (in FIGS.
10-12, 15 and 16), it will be appreciated that the grid polarizer
can be used with a transmissive spatial light modulator 168, as
shown in FIGS. 13 and 14. The transmissive spatial light modulator
can be a high-temperature polysilicon (HTPS) panel.
[0078] Although a projection system and modulation optical system
were shown in FIGS. 10-13 with the beam splitter in reflection mode
(or with the image reflecting from the beam splitter), it will be
appreciated that a projection system 100b or modulation optical
system 150b or 164b can be configured with the beam splitter in
transmission mode (or with the image transmitting through the beam
splitter), as shown in FIGS. 14, 15 and 16.
[0079] Referring to FIG. 14, a projection system 164b is shown with
a transmissive spatial light modulator 168 and a beam splitter 102
used in transmission mode (or with the image transmitted through
the beam splitter). It is believed that such a configuration can
take advantage of the improved transmission contrast of the beam
splitter 102.
[0080] Various aspects of projection display systems with wire-grid
polarizers or wire-grid polarizing beam splitters are shown in U.S.
Pat. Nos. 6,234,634; 6,447,120; 6,666,556; 6,585,378; 6,909,473;
6,900,866; 6,982,733; 6,954,245; 6,897,926; 6,805,445; 6,769,779
and U.S. patent application Ser. Nos. 10/812,790; 11/048,675;
11/198,916; 10/902,319; which are herein incorporated by
reference.
[0081] Although a rear projection system has been described herein
it will be appreciated that a projection system can be of any type,
including a front projection system.
[0082] The above descriptions of the grid polarizer and various
applications have been directed to visible light (.about.400
nm-.about.700 nm). It will be appreciated, however, that a grid
polarizer can be configured for use in infrared light
(>.about.700 nm) and ultra-violet light (<.about.400 nm) and
related applications. Such a grid polarizer can have a larger
period and thicker layers.
[0083] For example, referring to FIG. 17, an inorganic, dielectric
grid polarizer 210 can be configured for use in infrared light, for
applications such as telecommunications. The grid polarizer 210 is
similar to those described above, and the above description is
incorporated herein. The grid polarizer 210 has at least one film
layer that is discontinuous to form a form birefringent layer with
an array 226 of parallel ribs 230. The ribs have a pitch or period
less than the wavelength being treated. For infrared applications
(.lamda..apprxeq.1300-1500 nm), such as telecommunication systems,
the ribs can have a pitch or period less than 1 micron (1 .mu.m or
1000 nm) in one aspect, or less than 0.4 microns (0.40 .mu.m or 400
nm) in another aspect; but greater than 0.20 microns or micrometers
(0.20 .mu.m or 200 nm). Thus, an incident light beam L incident on
the polarizer 210 separates the light into two orthogonal
polarization orientations, with light having s-polarization
orientation being reflected, and light having p-polarization
orientation being transmitted or passed. (It is of course
understood that the separation, or reflection and transmission, may
not be perfect and that there may be losses or amounts of undesired
polarization orientation either reflected and/or transmitted.) In
addition, it will be noted that the array or grid of ribs with a
pitch less than about half the wavelength of light does not act
like a diffraction grating (which has a pitch about half the
wavelength of light).
[0084] Such a grid polarizer 210 has low insertion loss, or little
absorption. Thus, the grid polarizer 210 can be inserted into an
optical train of a telecommunication application in which low
insertion losses is important.
[0085] Referring to FIG. 18a, a combiner 240 is shown with a grid
polarizer 210 described above. The combiner 200 includes a grid
polarizer 210 as described above disposed between
collimating/focusing lenses 244, such as graded index lenses, that
can be oriented in a coaxial configuration so that their optical
axes align to define an optical axis. First and second optical
input fibers (or first and second optical beam carriers) 248 and
252 are disposed on opposite sides of the combiner and oriented
parallel to the optical axis. An optical output fiber (or optical
beam carrier) 254 is disposed adjacent to the first input fiber 248
at an end of the lens and oriented parallel to the optical axis.
The fibers can be polarizing maintaining fibers. The first input
fiber 248 can contain a polarized beam of s-polarization
orientation while the second input fiber 252 can contain a
polarized beam of p-polarization orientation. The grid polarizer
210 combines the beams into an output beam in the output fiber 254.
The reflected beam and the transmitted beam combine to form a
composite depolarized output beam having both polarization
states.
[0086] Referring to FIG. 18b, a separator 260 is shown with a grid
polarizer 210. The separator 260 includes a grid polarizer 210 as
described above disposed between collimating/focusing lenses 244,
such as graded index lenses, that can be oriented in a coaxial
configuration so that their optical axes align to define an optical
axis. First and second optical output fibers (or first and second
optical beam carriers) 262 and 266 are disposed on opposite sides
of the combiner and oriented parallel to the optical axis. An
optical input fiber (or optical beam carrier) 270 is disposed
adjacent to the first output fiber 262 at an end of the lens and
oriented parallel to the optical axis. The fibers can be polarizing
maintaining fibers. The input fiber 270 can contain an unpolarized
beam. The grid polarizer 210 splits the beams into a reflected beam
of s-polarization orientation directed towards the first output
fiber, and a transmitted beam of p-polarization orientation
directed towards the second output fiber.
[0087] As another example, referring to FIG. 19, an inorganic,
dielectric grid polarizer 310 can be configured for use in visible
and/or near visible or near infrared, for applications such as
optical drives or optical data storage. Data storage devices can
include read only devices and read and write devices. Examples of
such optical drives include compact disc (CD) drives, digital video
disc (DVD) drives, high-density digital video disc (HD-DVD) blu-ray
disc (BD) drives, etc. CD drives typically use 780 nm light. DVD
drives typically use 650 nm light. HD-DVD or BD drives typically
use 405 nm light. Combination drives can utilize all three
wavelengths. The grid polarizer 310 is similar to those described
above, and the above description is incorporated herein. The grid
polarizer 310 has at least one film layer that is discontinuous to
form a form birefringent layer with an array 326 of parallel ribs
330. For combination drives, the ribs can have a pitch or period
less than 780 nm in one aspect, or less than 390 nm in another
aspect. The grid polarizer 310 has low insertion loss.
[0088] Referring to FIG. 20, an optical data storage system 350 is
shown including a grid polarizer 310 as described above. The data
storage system can be configured to operate with one or more
standard formats, including for example, compact disc (CD), digital
video disc (DVD), high-density digital video disc (HD-DVD or
Blu-Ray), or combinations of the above. A laser diode 354 can
produce one or more light beams. The wavelength of the light beam
can depend on desired use. For example, CDs commonly use light with
780 nm wavelength; DVDs commonly use light with 650 nm wavelength;
and HD-DVD or Blu-Ray commonly use light with 405 nm wavelength.
The laser diode can produce one or more, or all, of these
wavelengths. The light beam is directed at a grid polarizer 310,
which can polarizer the light, or pass polarized light beam. The
grid polarizer 310 can be configured for use with the wavelength of
the light produced by the laser diode. One or more grid polarizers
310 can be provided if more than one different wavelength of light
is used. For example, the grid polarizers can have different
periods configured for the wavelength used. The one or more grid
polarizers 310 can have ribs with a pitch less than half of 780 nm,
650 nm and/or 405 nm. The light beam from the grid polarizer is
incident on a disc medium 358, such as a plastic disc with an
aluminum layer therein, as is known in the art. A motor or drive
360 can turn or rotate the disc medium 358. The light beam or laser
diode can be moved radially across the disc medium as it is
rotated. The disc medium 358 can reflect a modified light beam
based on bumps in an aluminum layer in the disc, as known in the
art, and can change the polarization orientation of the light beam.
In addition, the disc medium can reflect a modified light beam
based on dye in the disc, as is known in the art, and can change
the polarization orientation of the light beam. The light beam
reflected by the disc is directed towards the grid polarizer which
separates the light beam based on polarization orientation. The
separated light beam can be directed towards a photo-detector 364,
as is known in the art. The photo-detector can be disposed in the
reflected beam, as shown, or in the transmitted beam. In addition,
various optics and lenses can treat or direct the beams.
[0089] A grid polarizer as described above can be used with a laser
system, such as being disposed in a laser cavity. The grid
polarizer has high heat tolerance. Such a laser system can produce
highly polarized light. The laser system can be used in an image
projection system.
[0090] Grid polarizers described above can be utilized in a light
recycling system. Such a light recycling system can be utilized in
an image projection system described above. It will be appreciated
that a beam of light includes two orthogonal polarization
orientations that are separated by the grid polarizers described
above. Thus, one polarization orientation, or approximately half of
the light, might be discarded. A light recycling system described
below can be employed to recover the other polarization
orientation, thus utilizing more or all of the available light.
Referring to FIG. 21a, a light recycling system 400 is shown
utilizing a grid polarizer (represented by 10) as described above.
The recycling system can include a light source 404 which can be of
any type, including arc lamps, LED arrays, etc. In addition, the
light source 404 can include a reflector. The light from the light
source is directed towards the grid polarizer 10 which separates
the polarization into two polarizations; reflecting the
s-polarization orientation oriented parallel with the ribs, and
transmitting p-polarization orientation oriented perpendicular to
the ribs. The reflected polarization can be directed towards one or
more reflectors 408, such as mirrors, and a light reorientation
means 412, such as a wave plate, for changing the polarization
orientation from s-polarization orientation to p-polarization
orientation. The system can be configured so that the reflected
light makes a single pass through the wave plate (illustrated by
solid lines) then the wave plate can be a half wave plate.
Alternatively, the system can be configured so that the reflected
light makes two passes through the wave plate (illustrated by
dashed lines) then the wave plate can be a quarter wave plate.
Alternatively, the reflected light can be directed back to the
reflector of the light source. After the light is converted from
s-polarization to p-polarization, it can be directed in the same
direction as the passed light beam and combined with the passed
light beam to form a single beam of a single polarization
orientation. The reflected and converted light can be passed
through the grid polarizer (indicated by the dashed lines) or can
bypass the grid polarizer.
[0091] Referring to FIG. 21b, another light recycling system 400b
is shown utilizing a grid polarizer (represented by 10) as
described above. Again, the light from the light source can be
directed through a polarization reorientation means 412, such as a
quarter wave plate, and to the grid polarizer 10. The reflected
s-polarization orientation can be reflected back through the
reorientation means to the light source which reflects it back
through the reorientation means. After passing through the
reorientation means, the light is converted from s-polarization
orientation to p-polarization orientation and passes through the
grid polarizer. Thus, substantially all the light has a single
polarization orientation.
[0092] Referring to FIG. 21c, another light recycling system 400c
is shown utilizing a grid polarizer (represented by 10) as
described above. The light from the light source can be directed
directly to the grid polarizer 10. The passes light of
p-polarization orientation can be passed through a reorientation
means 412, such as a half wave plate, to convert it to
p-polarization orientation. Thus, substantially all the light has a
single polarization orientation. In addition, both beams may be
combined into a single beam, and/or directed in a common direction,
such as by mirrors. In this configuration, light is not directed
back to the light source.
[0093] Referring to FIG. 21d, another light recycling system 400d,
is shown utilizing a grid polarizer (represented by 10) as
described above. The system 400d is similar to that described in
FIG. 21c, except that the reflected beam of s-polarization
orientation is passed through the reorientation means 412 to
convert it to p-polarization orientation.
[0094] Examples of light recycling systems are shown in U.S. Pat.
Nos. 6,108,131; 6,208,463; 6,452,724; and 6,710,921; which are
herein incorporated by reference.
[0095] With respect to FIGS. 21a-d, waveplates are examples of
light reorientation means for changing the polarization orientation
of the transmitted or reflected beam. In addition, mirrors and
reflectors are examples light combination means for changing a
direction of the transmitted or reflected beam so that both the
transmitted beam and the reflected beam are combined and have the
same direction.
[0096] While the forgoing examples are illustrative of the
principles of the present invention in one or more particular
applications, it will be apparent to those of ordinary skill in the
art that numerous modifications in form, usage and details of
implementation can be made without the exercise of inventive
faculty, and without departing from the principles and concepts of
the invention. Accordingly, it is not intended that the invention
be limited, except as by the claims set forth below.
* * * * *